Special Seminar: Big Pulsations in Small Stars: The Remarkable Population of Large-Amplitude Hot-Subdwarf Pulsators
- When
- Wednesday, November 11, 20263:30 PM – 4:30 PM ESTAdd to calendarGoogle Calendar
- Where
- 207 Phillips HallOpen in Maps
- Hosted by
- Physics and Astronomy
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About
Speaker: Corey Bradshaw (University of Hamburg)
Title: Big Pulsations in Small Stars: The Remarkable Population of Large-Amplitude Hot-Subdwarf Pulsators
Abstract: B-type hot subdwarfs (sdBs) are a rare class of evolved stars occupying a sparsely populated region of the Hertzsprung–Russell diagram. Their existence is not readily explained by standard single-star evolutionary channels, indicating that binary interactions play a key role in their formation. In recent years, several classes of sdB-like stars have been found to exhibit remarkably large-amplitude, short-period pulsations dominated by low-order radial modes. These include radial-mode sdB variables (rm-sdBVs) and blue large-amplitude pulsators (BLAPs). The most extreme examples, the BLAPs, undergo dramatic changes in radial velocity, effective temperature, and surface acceleration as their radii vary drastically over short pulsation cycles of less than an hour. These pulsations can even be violent enough to generate shocks in the stellar atmosphere during phases of extreme compression. Despite their extraordinary behavior, the evolutionary origins of these objects remain largely unconstrained. Proposed formation pathways include envelope stripping by a binary companion, white-dwarf mergers, and even the surviving companions of Type Ia supernovae. These scenarios predict different stellar mass ranges and evolutionary states, making detailed spectroscopic observations essential for measuring their properties and distinguishing among their proposed origins. In this talk, I will present results from recent observational studies of large-amplitude hot-subdwarf pulsators. I will examine the observational and physical distinctions between the rm-sdBV and BLAP classes, characterize their extreme pulsation dynamics, and discuss how measurements of their physical properties can constrain the evolutionary pathways responsible for their formation.